*: Address comment

optimizer/plan/planbuilder.go

@@ -119,7 +119,7 @@ func (b *planBuilder) extractSelectAgg(sel *ast.SelectStmt) []*ast.AggregateFunc
 		for _, item := range sel.OrderBy.Items {
 			n, ok := item.Expr.Accept(extractor)
 			if !ok {
-				b.err = errors.New("Failed to extract agg expr from orderbyu clause")
+				b.err = errors.New("Failed to extract agg expr from orderby clause")
 				return nil
 			}
 			item.Expr = n.(ast.ExprNode)
@@ -131,7 +131,8 @@ func (b *planBuilder) extractSelectAgg(sel *ast.SelectStmt) []*ast.AggregateFunc
 
 func (b *planBuilder) buildSelect(sel *ast.SelectStmt) Plan {
 	var aggFuncs []*ast.AggregateFuncExpr
-	if b.detectSelectAgg(sel) {
+	hasAgg := b.detectSelectAgg(sel)
+	if hasAgg {
 		aggFuncs = b.extractSelectAgg(sel)
 	}
 	var p Plan
@@ -152,15 +153,15 @@ func (b *planBuilder) buildSelect(sel *ast.SelectStmt) Plan {
 				return nil
 			}
 		}
-		if len(aggFuncs) > 0 || sel.GroupBy != nil {
+		if hasAgg {
 			p = b.buildAggregate(p, aggFuncs, sel.GroupBy)
 		}
 		p = b.buildSelectFields(p, sel.GetResultFields())
 		if b.err != nil {
 			return nil
 		}
 	} else {
-		if len(aggFuncs) > 0 {
+		if hasAgg {
 			p = b.buildAggregate(p, aggFuncs, nil)
 		}
 		p = b.buildSelectFields(p, sel.GetResultFields())

optimizer/resolver.go

@@ -308,15 +308,16 @@ func (nr *nameResolver) resolveColumnNameInContext(ctx *resolverContext, cn *ast
 			}
 			return nr.resolveColumnInResultFields(cn, ctx.fieldList)
 		}
-		// Resolve from table first, than from select list.
+		// Resolve from table first, then from select list.
 		found := nr.resolveColumnInTableSources(cn, ctx.tables)
+		if nr.Err != nil {
+			return found
+		}
 		// We should copy the refer here.
 		// Because if the ByItem is an identifier, we should check if it
 		// is ambiguous even it is already resolved from table source.
 		// If the ByItem is not an identifier, we do not need the second check.
 		r := cn.Refer
-		pe := nr.Err
-		nr.Err = nil
 		if nr.resolveColumnInResultFields(cn, ctx.fieldList) {
 			if nr.Err != nil {
 				return true
@@ -328,8 +329,6 @@ func (nr *nameResolver) resolveColumnNameInContext(ctx *resolverContext, cn *ast
 			}
 			return true
 		}
-		// Restore err.
-		nr.Err = pe
 		return found
 	}
 	if ctx.inHaving {